It is planned to study the mechanisms which produce defective energy metabolism in the Ac rabbit and in human achondroplasia. In addition, studies of other hyman chondrodystrophies, notably achondrogenesis and thanatophoric dwarfism will be performed to determine if defective energy metabolism is present and, if so, the mechanisms underlying the defects will be studied. Finally, we will continue our studies on the effects of age on mitochondrial function to determine if these effects are reversible.